Please specify few best site to stay up to date with web design.
I usually check http://www.smashingmagazine.com/ every once in a while.
I have found that when you search for something you need to do and find a good tutorial, you should bookmark the blog or website because that person will typically post more content.
Here is a pretty good list of web development blogs to follow,
There are tons a brilliant people out there posting amazing stuff. If you look on Twitter, you'll see lots of interesting stuff. Sites like A List Apart are worth following.
If you feel that you are advanced enough, then I would float ( pun intended), more towards http://www.netmagazine.com/.